/*
 * FieldContact.java April 2007
 *
 * Copyright (C) 2007, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.core;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;

import wx.xml.simpleframework.xml.util.Cache;
import wx.xml.simpleframework.xml.util.ConcurrentCache;

/**
 * The <code>FieldContact</code> object is used to act as a contact
 * for a field within an object. This allows a value to be set on an
 * object field during deserialization and acquired from the same
 * field during serialization.
 *
 * @author Niall Gallagher
 * @see wx.xml.simpleframework.xml.core.FieldScanner
 */
class FieldContact implements Contact {

    /**
     * This cache contains the annotations present on the field.
     */
    private final Cache<Annotation> cache;

    /**
     * This is the list of annotations associated with the field.
     */
    private final Annotation[] list;

    /**
     * This is the label that marks the field within the object.
     */
    private final Annotation label;

    /**
     * This represents the field within the schema class object.
     */
    private final Field field;

    /**
     * This is the name for this contact as taken from the field.
     */
    private final String name;

    /**
     * This is the modifiers for the field that this represents.
     */
    private final int modifier;

    /**
     * Constructor for the <code>FieldContact</code> object. This is
     * used as a point of contact for a field within a schema class.
     * Values can be read and written directly to the field with this.
     *
     * @param field this is the field that is the point of contact
     * @param label this is the annotation that is used by the field
     * @param list  this is the list of annotations on the field
     */
    public FieldContact(Field field, Annotation label, Annotation[] list) {
        this.cache = new ConcurrentCache<Annotation>();
        this.modifier = field.getModifiers();
        this.name = field.getName();
        this.label = label;
        this.field = field;
        this.list = list;
    }

    /**
     * This is used to determine if the annotated contact is for a
     * read only variable. A read only variable is a field that
     * can be set from within the constructor such as a blank final
     * variable. It can also be a method with no set counterpart.
     *
     * @return this returns true if the contact is a constant one
     */
    public boolean isReadOnly() {
        return !isStatic() && isFinal();
    }

    /**
     * This is used to determine if the annotated contact is for a
     * static field or method. A static field or method is one that
     * contains the "static" keyword. Any static final fields will
     * be read only and does not require any matching annotation.
     *
     * @return this returns true if the contact is a static one
     */
    public boolean isStatic() {
        return Modifier.isStatic(modifier);
    }

    /**
     * This is used to identify annotated methods are fields that
     * can not be modified. Such field will require that there is
     * a constructor that can have the value injected in to it.
     *
     * @return this returns true if the field or method is final
     */
    public boolean isFinal() {
        return Modifier.isFinal(modifier);
    }

    /**
     * This will provide the contact type. The contact type is the
     * class that is to be set and get on the object. This represents
     * the return type for the get and the parameter for the set.
     *
     * @return this returns the type that this contact represents
     */
    public Class getType() {
        return field.getType();
    }

    /**
     * This provides the dependent class for the contact. This will
     * actually represent a generic type for the actual type. For
     * contacts that use a <code>Collection</code> type this will
     * be the generic type parameter for that collection.
     *
     * @return this returns the dependent type for the contact
     */
    public Class getDependent() {
        return Reflector.getDependent(field);
    }

    /**
     * This provides the dependent classes for the contact. This will
     * typically represent a generic types for the actual type. For
     * contacts that use a <code>Map</code> type this will be the
     * generic type parameter for that map type declaration.
     *
     * @return this returns the dependent type for the contact
     */
    public Class[] getDependents() {
        return Reflector.getDependents(field);
    }

    /**
     * This is the class that declares the contact. The declaring
     * class is where the field represented been defined. This will
     * typically be a class rather than an interface.
     *
     * @return this returns the class the contact is declared within
     */
    public Class getDeclaringClass() {
        return field.getDeclaringClass();
    }

    /**
     * This is used to acquire the name of the field. This will return
     * the name of the field which can then be used to determine the
     * XML attribute or element the contact represents. This ensures
     * that the name provided string is internalized for performance.
     *
     * @return this returns the name of the field represented
     */
    public String getName() {
        return name;
    }

    /**
     * This is the annotation associated with the point of contact.
     * This will be an XML annotation that describes how the contact
     * should be serialized and deserialized from the object.
     *
     * @return this provides the annotation associated with this
     */
    public Annotation getAnnotation() {
        return label;
    }

    /**
     * This is the annotation associated with the point of contact.
     * This will be an XML annotation that describes how the contact
     * should be serialized and deserialized from the object.
     *
     * @param type this is the type of the annotation to acquire
     * @return this provides the annotation associated with this
     */
    public <T extends Annotation> T getAnnotation(Class<T> type) {
        if (type == label.annotationType()) {
            return (T) label;
        }
        return getCache(type);
    }

    /**
     * This is the annotation associated with the point of contact.
     * This will be an XML annotation that describes how the contact
     * should be serialized and deserialized from the object.
     *
     * @param type this is the type of the annotation to acquire
     * @return this provides the annotation associated with this
     */
    private <T extends Annotation> T getCache(Class<T> type) {
        if (cache.isEmpty()) {
            for (Annotation entry : list) {
                Class key = entry.annotationType();
                cache.cache(key, entry);
            }
        }
        return (T) cache.fetch(type);
    }

    /**
     * This is used to set the specified value on the provided object.
     * The value provided must be an instance of the contact class so
     * that it can be set without a runtime class compatibility error.
     *
     * @param source this is the object to set the value on
     * @param value  this is the value that is to be set on the object
     */
    public void set(Object source, Object value) throws Exception {
        if (!isFinal()) {
            field.set(source, value);
        }
    }

    /**
     * This is used to get the specified value on the provided object.
     * The value returned from this method will be an instance of the
     * contact class type. If the returned object is of a different
     * type then the serialization process will fail.
     *
     * @param source this is the object to acquire the value from
     * @return this is the value that is acquired from the object
     */
    public Object get(Object source) throws Exception {
        return field.get(source);
    }

    /**
     * This is used to describe the contact as it exists within the
     * owning class. It is used to provide error messages that can
     * be used to debug issues that occur when processing a contact.
     * The string provided is the generic field string.
     *
     * @return this returns a string representation of the contact
     */
    public String toString() {
        return String.format("field '%s' %s", getName(), field.toString());
    }
}
